Long and arduous negotiations ended last night with an unexpected display of unity by the world's eight most powerful nations over how to handle the Middle East conflict, as they called for an end to the cross-border attacks that have left more than 150 people dead in five days.

The Group of Eight, meeting in St Petersburg, issued a call for both Israel and the "extremist forces" of Hamas and Hizbollah to halt their attacks, and for an additional UN security and monitoring force to move in to keep the peace in Lebanon when the Israelis pull out.

The statement called for attacks on Israel to end "immediately", and implied that Israel is entitled to retaliate if they continue.

George Bush and Tony Blair pulled off a coup by persuading Russia's President, Vladimir Putin, and France's Jacques Chirac to sign up to a statement that blamed the violence squarely on "extremists" on the Palestinian side.

The document also avoided using the word "ceasefire", which is what the Lebanese Prime Minister, Fouad Siniora, has pleaded for, with President Chirac's support. The US and Britain maintained that there cannot be a ceasefire which leaves Israel open to renewed attack. One concession by Mr Bush and Mr Blair is that there is no mention either of Iran and Syria, whom the two leaders identified as culprits in the Lebanon tragedy.

The deaths of eight Israeli civilians in Haifa, killed by an Iranian-built missile, is a reminder that the Prime Minister Ehud Olmert is facing, less than four months after winning an election, what could be the greatest test of his premiership. So far, the country has rallied behind him.

This is an operation that started because two soldiers had been seized - and three others killed - in a cross-border raid. It has now widened to much more than that - the goal of disabling the threat on Israel's northern border posed by Hizbollah.

And while the barrages of rockets intensify the crisis, they also have a dramatic demonstration effect - that Hizbollah is indeed the threat it has long been depicted as. The widely-discussed military failures to prevent the cross-border raid, the one in Kerem Shalom, and Friday's night's missile attack on a ship, have provoked strong criticism of the Israeli military, but not of Mr Olmert. And, finally, as Israeli officials repeatedly point out, whatever criticism there may be of the methods being used, the objective of disarming Hizbollah has been endorsed by the UN.

For Mr Olmert, therefore, this crisis is an opportunity as well as a threat. As a man without the military experience of his most recent predecessors, he, and even more exceptionally in that respect, his Defence Minister, Amir Peretz, have something to prove. Neither Ehud Barak nor Ariel Sharon were above sorting out abductions without resorting to force on this scale. With hindsight, there were criticisms of both for setting about the comprehensive task of eliminating the Hizbollah threat as Mr Olmert is now seeking to do.